As far as advancing through the darkside PVE missions you're going to have to at the very least unlock Daka if you want to max the gear on some of your toons. It's pretty much a necessity. But you dont have to invest any further in her once unlocked as a 4* Daka does fine in PVE. It wouldnt hurt to 5 star her tho since you're so close.
Boba is one of the most well rounded characters in the game. One of only 3 characters you can advance to the second epic tier atm. But many people use him in a jedi or single target DPS team comp & and he really doesn't do as well synergy wise in those types of teams. So most write Boba off. But in an AOE heavy team Boba is a god. He is durable, has highest DPS of all tanks, self rez and he just got buffed. Poe is the sleeper, he could be awesome but theres not enough information on him atm to make a judgement.